title: Precipitating anti-VIII:C antibodies in two patients with haemophilia A.
abstract: IgG from the plasmas of two haemophilia A patients with anti-VIII:CAg antibodies (1000 and 200 u/ml) was isolated and labelled with 125I. The specific labelled anti-VIII:CAg IgG was further purified by binding to and elution from immobilized factor VIII/von Willebrand factor (F.VIII/vWF). When studied by immunodiffusion and autoradiography, both antibodies gave a precipitin line with normal plasma, serum, cryoprecipitate, purified F.VIII/vWF and the plasmas of two patients with haemophilia A+. No precipitin line was observed with the plasmas of 11 patients with haemophilia A- or four patients with severe von Willebrand's disease. Levels of VIII:CAg obtained by radioelectroimmunoassay were in agreement with those obtained by immunoradiometric assay. This study demonstrates that, contrary to previous evidence, human anti-VIII:CAg antibodies are precipitating as well as neutralizing when studied by highly sensitive techniques.
mesh_terms: D000906:Antibodies / Q000032:analysis*; D000941:Antigens / Q000276:immunology; D005169:Factor VIII / Q000276:immunology*; D006467:Hemophilia A / Q000276:immunology*; D006801:Humans; D005779:Immunodiffusion; D007074:Immunoglobulin G / Q000032:analysis; D011233:Precipitin Tests; D011863:Radioimmunoassay; D014842:von Willebrand Diseases / Q000276:immunology; D014841:von Willebrand Factor / Q000276:immunology
chemical_list: D000906:Antibodies; D000941:Antigens; D007074:Immunoglobulin G; D014841:von Willebrand Factor; D005169:Factor VIII